Dr Mike Ryan, the WHO's emergencies head, said the figure could be higher without concerted international action.
Almost one million people have died with Covid-19 worldwide since the disease first emerged in China late last year.
Virus infections continue to rise, with 32 million cases confirmed globally.
The start of a second surge of coronavirus infections has been seen in many countries in the northern hemisphere as winter approaches.
So far, the US, India and Brazil have confirmed the most cases, recording more than 15 million between them.